Go to Controllers > Wii Remote 1 > Configure > NSMBW only uses the remote sideways.
Manually mapping buttons works, but if you want a truly optimized, professional setup, you should import a dedicated controller profile. dolphin new super mario bros wii xbox controller
Change the dropdown menu from "Real Wii Remote" to . Go to Controllers > Wii Remote 1 >
Map to X (or B ) on your Xbox controller. (This acts as your Run/Dash/Fireball button). Go to Controllers >